Trip Truck

big world - short life

Box Construction

Heavy! more or less sums this part of the project up. Each of the larger panels was a struggle for four moderately bulky blokes to carry around. Consequently there were time delays involved that I’d not anticipated in getting on with the build.

Nevertheless, the panels were slowly but surely assembled in the order that I’d worked out would be best. The bulkhead panel was first just mocked into place which allowed the floor to be laid accurately in position. The floor panel needed a slight buzz-over with a power plane on a couple of edges but otherwise dropped neatly onto the bed. This was then glued down using Sikaflex 252 (chosen for its very high bonding strength). Once in position, the floor then set up a fairly-easy-to-align (if difficult to muscle into position) build process for the rest of the panels.

The bulkhead and then sidewalls were the first to be bonded into place, followed by the roof, rear upper panel, and finally the rear lower panel. Sikaflex 252 was used as the main bonding medium on all of the panels but was supplemented with Sikaflex 512 which was retrospectively pumped into any gaps to fully seal and further bond all the joints. As Sikaflex needs to retain some ‘volume’ to work properly (it doesn’t bond if squished out of a joint) I used wafer headed screws at strategic locations around the build to make sure that the closest the panels could register would be 2mm. This was one of the headaches that had to be overcome at the design stage and I had to revise my original dimensions to accommodate the ‘box expansion’ caused by factoring the adhesive’s requirement in. Aluminium cappings were finally bonded to the perimeter of the box to protect and weatherproof the exposed edges.

With great credit to CVR and Transport Windows, the panels and doors popped into place without hardship. I had anticipated needing to spend time to get everything to fit properly but, apart from squaring off the floor, it just wasn’t the case. Even the window apertures were absolutely spot on allowing the Seitz windows to slip in without any drama whatsoever.

Doors and Windows

Seitz S4 windows are used throughout the motorhome industry and work very well. Being fully self contained, double ‘glazed’ and having a sunshade and fly screen built in, they are a godsend to self-builders. The inner and outer frames simply screw together sandwiching the wall panel between them; providing the wall is between 1 and 53mm thick. In reality it’s possible to fix them to thicker walls than this but Seitz only provide instructions to cover these extremes. Essentially the units are made to fit 26mm thick panels and depending whether your panels are actually thinner, or thicker than this, dictates where exactly on the frames you have to build up packing material. The instructions that come with the windows fully explain the process. In our case I had to build strips of 4mm thick material of 32mm width and bond them to the outer frame. I chose aluminium from Metals4U but it's possible to use timber or plastic if preferred. Once packed out the windows are bedded on a non-setting mastic and simply screwed into place. I used Carafax IDL99 but some prefer mastic tape. The critical thing is to use non-setting sealant to allow removal at a later stage if necessary. Our particular indows were supplied by O'Briens, who stock a huge range of sizes and were quick with delivery. We chose the sliding version of the windows as these can be left open when the vehicle is moving and also allow internal operation of our self-fabricated, protective ‘hinge-down’ aluminium covers. These covers are primarily intended to stop damage to the windows, but also help with better security. Anyone that has driven a Seitz window within a foot of overhanging vegetation will know that the acrylic they are made of is ridiculously vulnerable to scratching and very easily ruined.

The doors were simply Sikaflexed into place and finished on the inside edges with some angled aluminium, suitably mitred and stuck into place. Only one slight modification to the garage doors was required at this stage, and that was to bond a piece of profiled aluminium to the top outside edge to keep water from running directly down the walls and onto the seals. Without this water would - in sufficient quantities - easily work itself past the standard (double) door seals.

The whole process, though time consuming to get just right, wasn’t that difficult. Anyone worried about building a box of their own shouldn’t be put off. The critical thing is to do the hard work at the design stage. Also, having all the door and window apertures cut by the panel manufacturer was definitely the right choice for me at least, saving much time and side-stepping the potential for jigsaw-related disasters.